The present invention relates to methods and systems for treating organic waste, which include determining the ignition threshold temperature for the organic waste and one or more mineral by-products, selecting a ratio of organic waste:mineral by-product based on the determined ignition threshold temperature, combining the mineral by-product(s) with the organic waste, so as to arrive at a mixture having the selected ratio of organic waste:mineral by-product(s); and drying the mixture of organic waste and mineral by-product(s) to produce organic waste solids.
The present invention also relates to organic waste solids formed by the methods of the present invention.
Mineral by-products have been used in stabilizing semi-solid, odorous organic waste through bulk drying, odor absorption, and granulation (see e.g., U.S. Pat. Nos. 3,877,920 and 4,554,002). In addition, mineral materials including sand, diatomaceous earth, perlite, and various mineral reagent powders have been used in conjunction with fluidized heating, drying and burning of sludges and oily waste (see e.g., U.S. Pat. Nos. 4,159,682, 4,787,323, 4,970,803, 5,490,907). However, existing thermal dryers have ongoing problems with drying waste high in organics, particularly sewage sludges, in the waste sticking to dryer surfaces, charring and producing burnt organic matter odors, and catching on fire.
Therefore, a method of stabilizing organic waste without causing the ignition, sticking and/or production of burnt organic matter odors, caused by previously known methods, is desirable.
The present invention relates to methods and systems for treating organic waste. The present methods first require determining the ignition threshold temperature for the organic waste and one or more mineral by-products. The ignition threshold temperature is determined by plotting the ignition temperature of a mixture of a sample of the organic waste with a sample of the mineral by-products to be added to the organic waste. The plot indicates a threshold dose rate of mineral by-product to inhibit spontaneous ignition of the organic waste. Based on the ignition threshold temperature determined from the plot, a ratio of organic waste:mineral by-product(s) is selected for the actual (larger scale) process and the mineral by-product(s) is mixed with the organic waste so as to arrive at a mixture having the selected ratio of organic waste:mineral by-product(s). The mixture is then dried (or stored first and then dried) to arrive at organic waste solids, which are at least 60%, preferably at least 90%, more preferably at least 95% dried.
The treatment methods of the present invention are methods of stabilizing the treated organic waste so as to control the tendency of the organic waste to ignite for example, in external heat dryers.
The present invention is further directed to organic waste solids produced by the present methods, which are advantageous in not having a tendency to ignite.